Two different types of human mast cells have been identified and termed T (tryptase positive, chymase negative) and TC (tryptase positive, chymase positive); the purpose of the proposed research is to further characterize these cell types. Monoclonal antibodies will be produced against tryptase, chymase and carboxypeptidase (mast cell neutral proteases) to be used to better elucidate the cellular distribution of theses enzymes by immunohistochemical techniques and to quantify the cellular levels of each by immunoassay. Molecular RNA probes complementary to the mRNA of these proteases will be prepared and utilized to examine expression of this mRNA in mature and immature mast cells. The proteoglycan type synthesized by each cell type will be determined by analyzing the 35S-SO4 labeled proteoglycan produced and released by purified preparations of these cells. Monoclonal antibodies also will be produced against both surface and intracellular components of these cells by immunization with dispersed/enriched preparations of T and TC mast cells from adult and newborn tissues. Antibodies against mast cells form adult tissues should permit better definition of unique and shared components of these mast cell types. Antibodies against mast cells from newborn foreskin may identify markers of immature mast cells that will permit precursors of mast cells to be detected and characterized. Proof of whether or not a cell is a mast cell precursor will depend on showing in vitro that it can develop differentiated features of mast cells, such as the presence of histamine and tryptase. The ultrastructural features of mature and immature forms of T and TC types of mast cells as well as the subcellular localization of the interesting antigenic determinants recognized by the monoclonal antibodies will be analyzed by electron microscopic techniques. Finally, the concentration and distribution of T and TC types of mast cells will be determined indifferent pathologic conditions, including rheumatoid arthritis, scleroderma, allergic rhinitis, atopic dermatitis, systemic mastocytosis/urticaria pigmentosa, cystic fibrosis, breast and lung solid tumors and AIDS. Because T and TC types of mast cells appear to secrete both common and different mediators, develop along distinct pathways, respond differently to certain nonimmunologic secretagogues and pharmacologic agents and localize differently to different tissues their further characterization is crucial toward better understanding the role of these enigmatic cells to human health and disease.